1. Field of the Invention
The present invention relates to a vaporizer for generating a process gas from a liquid material, and a semiconductor processing system. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an LCD (Liquid Crystal Display) or FPD (Flat Panel Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
A film formation process for forming a predetermined film on the surface of a semiconductor wafer is performed in manufacturing semiconductor devices. For example, a process of this kind is performed, using a low-pressure CVD (Chemical Vapor Deposition) apparatus. In low-pressure CVD apparatuses, a source material is supplied in a gaseous state to promote a chemical reaction, thereby depositing a thin film on the surface of a wafer. In apparatuses of this kind, there is a case where a process gas is generated by vaporizing a liquid material, and is supplied into a process chamber as a film formation gas.
Examples of a film formation process using a process gas generated by vaporizing a liquid material are as follows. Specifically, a process gas generated by vaporizing TEOS (tetraethoxysilane) and oxygen (O2) gas are used to form an SiO2 film. A process gas generated by vaporizing Si2Cl6 and ammonia (NH3) gas are used to form a silicon nitride (Si3N4) film.
Patent Document 1 (Jpn. Pat. Appln. KOKAI Publication No. 3-126872 (Page 3, Paragraph number 30, and FIG. 1)) discloses one type of a vaporizer for vaporizing a liquid material. According to this vaporizer, an atomized liquid material is supplied from a nebulizer into a vaporizing chamber heated at a predetermined temperature, and is vaporized there. However, this vaporizer cannot provide a sufficient heat exchange when the atomized liquid material flows through the vaporizing chamber. Consequently, the process gas obtained at the output pipe of the vaporizing chamber contains a lot of mist. Where the process gas is supplied into the reaction chamber of, e.g., a low-pressure CVD apparatus, the mist is deposited on the surface of a wafer and generates particles. Thus, the mist is a cause of particle generation on the wafer.
Patent Document 2 (Jpn. Pat. Appln. KOKAI Publication No. 6-310444 (Paragraph number 0123 and FIG. 13)) discloses another type of a vaporizer for vaporizing a liquid material. According to this vaporizer, a plurality of vaporizing plates with a heater built therein are disposed in a vaporizing chamber perpendicularly to the inner wall thereof so as to interfere with flows of the liquid material. The atomized liquid material collides with the vaporizing plates and is vaporized thereby. However, this vaporizer entails gas dead volumes at the proximal ends of the vaporizing plates (on the vaporizer sidewall). In the dead volumes, the atomized liquid material does not collide with the vaporizing plate but accumulates to generate mist. Consequently, it is difficult to completely prevent mist generation.